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tie down ropes - Hints to Homebuilders

Posted By:
Jim Heffelfinger
Homebuilder or Craftsman
256
Posts
43
#1 Posted: 6/30/2011 13:24:07

I have to comment on the HInts to home builders video on tie down ropes.

Types of rope:  Polypropylene,  nylon and cotton ?!  >>  Polypropylene, nylon and  polyester  -  finding cotton today will be difficult.  And there are many hi-tech lines on the market as well.

polyester aka dacron:  very low stretch - use yacht braid (double braid)  fairly long life  in UV and dirt. > 10 years outside

nylon:  relatively high stretch - comes in a laid line ( 3 strands twisted) & yacht braid.  laid line more stretchy. Braid better behaved when handling. and has longer life in the outdoors.  near equal to polyester for lifespan

Polypropylene:  In the marine world we use this line for it's high visibility and floating characteristics - only.  Polypro is extremely sensitive to UV -  loosing 50% of line strength in one season. IT IS 1/2 THE STRENGTH OF POLYESTER AND EVEN LESS FOR NYLON     It is also generally very slippery - allowing knots to slip.    It has one thing going for it... it's really cheap.  1/3 the cost of the other two.  For airports to use this line at the tie downs is a set up for failure and much grief.  Using this line for your aircraft tie down lines is a choice. Nylon - use a smaller lighter line   It's your choice.  

Newer ropes involve some exotic materials but the line strength goes way up.  Samson ropes  AS90, 1/4" line has a break load of 9700 pounds.  Cheap like polypro?  no, about $2.25/ft.  There are others that are a bit less leading edge and more reasonable  - with ratings well past that Homer Brand  polypropylene.  Space and weight are always serious considerations in aviation.  

Samson "super strong" nylon braid 1/4" 2,300 pounds. ~$0.35/ft

Cutting the line and finishing the ends - all the synthetic lines have a melt temperature and will fuse the ends.  Here is an easier way.  Use paper tape wrap where you want to cut and melt.  Cut through the taped line with a sharp  utility knife or single edge raiser blade. You now have two ends taped and ready to melt.   Now with the tape still on - melt the ends.  I use the electric stove as it has no open flame.  Peel the tape. 

 

I



David Gray
IAC MemberHomebuilder or CraftsmanUltralight EnthusiastAirVenture Volunteer
38
Posts
10
#2 Posted: 6/30/2011 22:49:35

When I watched this video a few hous ago my first thought was "That doesn't look like a polypropylene rope". Moot point. I had hoped it would be an inovative anchor. When I cut my plastic (nylon) lines, I use a heated (cherry red) utility knife to cauterize as it cuts. Sometimes the edges need touching up. I am going to try it.



Jim Heffelfinger
Homebuilder or Craftsman
256
Posts
43
#3 Posted: 7/1/2011 00:06:12

The polypro line in the video is a newer development for the line called MFP  multi fiber polypropylene.  it's the rope  variant of micro fiber material.  It has even more surface area and even more sensitive to UV.  



Jim Heffelfinger
Homebuilder or Craftsman
256
Posts
43
#4 Posted: 7/7/2011 01:56:30

I was at the Homer big box store today and noted the polypro line laying around in bins everywhere.  The stuff I noted was 3/8 and rated for under 500 #.  

I am not interested in tying  my plane down with such a poor performing line - no matter how inexpensive it is.  Better off using 1/4" of the run of the mill "golden" 

http://www.samsonrope.com/index.cfm?ind=1&app=4&rope=98&inst=1




Dave Stadt
Vintage Aircraft Association MemberYoung Eagles Pilot or VolunteerAirVenture Volunteer
39
Posts
21
#5 Posted: 7/7/2011 11:22:45

In the boating world you cal tell the amateurs because they use the bright yellow or blue poly.  The pros won't let it near their boats and the same for airplanes.   It lacks strength, deterioates rapidly and you cannot tie a knot that holds. 

 

 



Jim Heffelfinger
Homebuilder or Craftsman
256
Posts
43
#6 Posted: 7/13/2011 17:06:29

I have to correct myself.  The 3/8 rope from Homer's store is rated at 244 #  .   I have 1.8 mm line sitting on my office desk rated at  500#.